go锁实现代码同步执行：sync.WaitGroup和sync.Mutex

package main

import (
  "fmt"
  "sync"
)

var (
  sum  int
  wg   sync.WaitGroup
  lock sync.Mutex
)

func main() {
  wg.Add(2)
  go func() {
    defer wg.Done()
    lock.Lock()
    for i := 1; i <= 100000; i++ {
      sum += i
    }
    lock.Unlock()
  }()
  go func() {
    defer wg.Done()
    lock.Lock()
    for i := 1; i <= 100000; i++ {
      sum -= i
    }
    lock.Unlock()
  }()
  wg.Wait()
  fmt.Println(sum)
}